Inverse-designed broadband low-loss grating coupler on thick lithium-niobate-on-insulator platform

TL;DR

This paper presents an inverse-designed, broadband, low-loss grating coupler on a thick lithium-niobate-on-insulator platform, achieving high efficiency and wide bandwidth with simple fabrication.

Contribution

It introduces a novel inverse design approach for a high-performance grating coupler on a thick lithium-niobate platform, optimized for fabrication and broadband operation.

Findings

Peak coupling efficiency of -3.8 dB at 1574.93 nm

1-dB bandwidth of 71.7 nm

3-dB bandwidth over 120 nm

Abstract

A grating coupler on 700-nm-thick Z-cut lithium-niobate-on-insulator platform with high coupling efficiency, large bandwidth, and high fabrication tolerance is designed and optimized by inverse design method. The optimized grating coupler is fabricated with a single set of e-beam lithography and etching process, and it is experimentally characterized to possess peak coupling efficiency of -3.8 dB at 1574.93 nm, 1-dB bandwidth of 71.7 nm, and 3-dB bandwidth of over 120 nm.